Realism is a theory that suggests the necessity of anarchy on the world stage, while at the same time realist doctrine suggests that stability cannot be achieved only by a "balance of power". That said, are the doctrines of collective security and defense fundamentally different from realism or does the idea of ​​a "balance of power" mean that even the law anarchic realism is intended to seek order or, at the very least, is at the mercy of the forces of order its necessity? The evaluation of the limits of realism and the examination of security institutions "in practice" Collective and defense can hopefully clarify this point. It is therefore essential to define the fundamental principles of realism, collective defense and security in order to understand the differences between them and the possible correlating factors necessary for them. the global evolution of realism/neo-realism. Realism as defined actually applies to almost everything. Whether it is science, mathematics, ethics, or politics, the nature and application of realism can be applied. It is therefore essential to narrow the scope of individual studies of realism. For the purposes of this article, the focus will remain on realism only in terms of its application to international relations, of which it appears to be the most dominant theory.1 Also called "political realism", its antithesis is generally considered to be the liberalism. Political realism emphasizes the conflictual and competitive nature required of states seeking to remain stable and in constant positive evolution. Conversely, liberalism suggests the need for cooperation between states.2 The determining factor of realism is therefore the ever-present need for a state to look after its own well-being while promoting its... environment paper... ...exists in all as an integral and dominant aspect of humanity. Works cited “Collective security”. University of Colorado at Boulder. http://www.colorado.edu/conflict/peace/treatment/collsec.htm (accessed May 27, 2011). Gallis, Paul E. “USIA – NATO: Article V and collective defense”. Federation of American Scientists. http://www.fas.org/man/crs/97-717f.htm (accessed May 27, 2011). Kemos, Alexander. “Thucydides in the modern world”. Home page of the HR Network. http://www.hri.org/por/thucydides.html (accessed May 27, 2011). “Political Realism in International Relations (Stanford Study of Philosophy). » Stanford Encyclopedia of Philosophy. http://plato.stanford.edu/entries/realism-intl-relations/ (accessed May 27, 2011). “Realism (Stanford Study of Philosophy). » Stanford Encyclopedia of Philosophy. http://plato.stanford.edu/entries/realism/ (accessed May 27, 2011).